In EP 70 001 B2, a thermoplastic molding resin of semicrystalline polyamide and amorphous copolyamide is disclosed. In U.S. Pat. No. 4,410,661, thermoplastic polyamide blends of semicrystalline polyamide and amorphous copolyamides from isophthalic acid, terephthalic acid, hexamethylene diamine, and bis-(p-aminocyclohexyl)methane, as well as impact resistance modifiers of the olefinic or core-shell polymer type are described. The disadvantage of both molding resins is that objects made from them are very sensitive to hot--and in particular boiling--water; preforms from a molding resin with a semicrystalline polyamide fraction of 40% by weight or less, completely lose their form stability, and those with a semicrystalline polyamide fraction of greater than 40% by weight suffer a substantial reduction in their stiffness.
In U.S. Pat. No. 3,200,428, there are described glass fiber-reinforced polyamide blends based on partially semi-crystalline polyamides with a fraction of amorphous transparent polyamides constituting a maximum of 20% by weight. These polyamide blends also do not meet the requirements in the temperature range above 100.degree. C. and in a humid atmosphere.
In EP 325,030 A2, a polyamide mixture is taught having an especially low second-order transition temperature and improved gas barrier-properties; the mixture consists of a specific copolyamide and an aliphatic homopolyamide. Here, too, the mechanical properties under action of heat and moisture are insufficient.
In DE-OS 3 817 279 Al, thermoplastic molding compounds of an amorphous part-aromatic copolyamide, a semicrystalline polyamide, and up to 60% by weight of a rubber-elastic polymer are set forth. These molding compounds have the disadvantage of poor mechanical properties under the combined action of heat and water.